The Eurasian lactase persistence variantLCT-13910 C/T is associated withvitamin D levels in individuals living at high latitude, more so than exposureto sunlight

Abstract

Rapid selection of a genetic variant that confers continuous life-long lactase production in Europeans (LCT-13910 C/T) has been attributed to the advan-tages of acquiring nutrients from consuming milk without the disadvantages of lactose malabsorption. Individuals with this genetic lactase persistence (LP)variant generally consume more milk and have been shown to have higher levels of serum vitamin D. Vitamin D is the principal regulator of Ca absorptionand its synthesis in skin is dependent on UVB exposure. The primary aim of the present study was to compare serum vitamin D concentrations with LPvariant and to control for UVB exposure. Data from over 100 000 individuals living in Norway, a country with low UVB exposure, was retrospectivelyretrieved for comparison of genetic LP variant, serum 25-hydroxyvitamin D (25(OH)D) concentration and the time of year when serum samples weretaken. For comparison, a similar analysis was performed with a natural dairy micronutrient, namely vitamin B12. It was found that individuals with thegenetic LP variant had considerably higher levels of serum 25(OH)D (P<2×10−16, Cohen’sd=0·73) but lower levels of vitamin B12(P<2×10−16,Cohen’sd=0·11), compared with genetic lactase non-persistent individuals, even when controlled for seasonality, age and sex. The difference inserum 25(OH)D levels did not diminish in summer months, showing the role of vitamin D in LP variant selection in areas of low UVB irradiation.LP variant selection advantage through acquiring another dairy micronutrient, vitamin B12, was not observed.